The effect of Pediococcus acidilactici J17 with high-antioxidant activity on antioxidant, α‑tocopherol, β‑carotene, fatty acids, and fermentation profiles of alfalfa silage ensiled at two different dry matter contents

Abstract

The effects of inoculation of strain Pediococcus acidilactici J17 with high antioxidant activity and a widely used commercial inoculum of Lactobacillus plantarum MTD-1, on antioxidant status, concentrations of α‑tocopherol and β‑carotene, fatty acid composition and fermentation profiles of ensiled alfalfa prepared at two dry matter (DM) contents were investigated. Chopped fresh alfalfa was ensiled at two DM contents of approximately 300 (low DM) and 400 (high DM) g/kg fresh weight, and treated with distilled water (control), L. plantarumMTD-1 and P. acidilactici J17, respectively. Forages were ensiled in vacuum-sealed polyethylene bags containing 500 g wilted forage for 60 d, with 4 replicates for each treatment. All inoculants effectively improved fermentation profiles of silages and the silage with a high DM exhibited better effects on inhibiting proteolysis and lipid oxidation; however, the antioxidant strain P. acidilactici J17 had little influence on the fatty acid composition of alfalfa silage. Silages with a low DM had higher proportions of saturated fatty acid and monounsaturated fatty acid, and lower proportions of polyunsaturated fatty acid compared with the silages with a high DM. Extensive degradation of α-tocopherol and β-carotene in alfalfa occurred after ensiling. The concentration of α-tocopherol in control silage declined to almost half of its original concentration in fresh alfalfa. Concentrations of β-carotene in the control silages with the low and high DM were accounted for 1/3 and 1/2 of their original concentrations in fresh alfalfa, respectively. In comparison with control silage and silage treated with L. plantarum MTD-1, inoculation of P. acidilactici J17 with high-antioxidant activity markedly increased the total antioxidant capacity (T-AOC), catalase (CAT) activity and concentrations of α-tocopherol and β-carotene of alfalfa silage ensiled at both DM contents. On average, higher T-AOC was observed in silage with a high DM than silage with a low DM. However, both inoculants decreased superoxide dismutase (SOD) activity of ensiled alfalfa. These results indicated that the P. acidilactici J17 strain could be used as a candidate antioxidant inoculum to improve the antioxidant status of alfalfa silage.